The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532-1293, USA.
Ann Bot. 2013 Aug;112(3):515-26. doi: 10.1093/aob/mct119. Epub 2013 May 30.
The sedge genus Carex, the most diversified angiosperm genus of the northern temperate zone, is renowned for its holocentric chromosomes and karyotype variability. The genus exhibits high variation in chromosome numbers both among and within species. Despite the possibility that this chromosome evolution may play a role in the high species diversity of Carex, population-level patterns of molecular and cytogenetic differentiation in the genus have not been extensively studied.
Microsatellite variation (11 loci, 461 individuals) and chromosomal diversity (82 individuals) were investigated in 22 Midwestern populations of the North American sedge Carex scoparia and two Northeastern populations.
Among Midwestern populations, geographic distance is the most important predictor of genetic differentiation. Within populations, inbreeding is high and chromosome variation explains a significant component of genetic differentiation. Infrequent dispersal among populations separated by >100 km explains an important component of molecular genetic and cytogenetic diversity within populations. However, karyotype variation and correlation between genetic and chromosomal variation persist within populations even when putative migrants based on genetic data are excluded.
These findings demonstrate dispersal and genetic connectivity among widespread populations that differ in chromosome numbers, explaining the phenomenon of genetic coherence in this karyotypically diverse sedge species. More generally, the study suggests that traditional sedge taxonomic boundaries demarcate good species even when those species encompass a high range of chromosomal diversity. This finding is important evidence as we work to document the limits and drivers of biodiversity in one of the world's largest angiosperm genera.
莎草属（Carex）是北温带分布最广的被子植物类群之一，以其着丝粒中心染色体和染色体组型的可变性而闻名。该属的染色体数目在种间和种内均存在高度变异。尽管这种染色体进化可能在莎草属的高物种多样性中发挥作用，但该属在种群水平上的分子和细胞遗传学分化模式尚未得到广泛研究。
在北美莎草属 Carex scoparia 的 22 个中西部种群和 2 个东北部种群中，调查了微卫星变异（11 个位点，461 个个体）和染色体多样性（82 个个体）。
在中西部种群中，地理距离是遗传分化的最重要预测因子。在种群内，近交程度高，染色体变异解释了遗传分化的重要组成部分。种群间>100km 的不频繁扩散解释了种群内分子遗传和细胞遗传多样性的重要组成部分。然而，即使排除基于遗传数据的假定迁移者，在种群内仍然存在着染色体变异和遗传变异与染色体变异之间的相关性。
这些发现表明，具有不同染色体数目的广泛分布的种群之间存在扩散和遗传连通性，这解释了该具有多种染色体形态的莎草物种中遗传一致性的现象。更普遍地说，该研究表明，传统的莎草分类边界即使在那些物种包含高度的染色体多样性时，也能很好地划分物种。这一发现是一个重要的证据，因为我们努力记录世界上最大的被子植物类群之一的生物多样性的限制和驱动因素。
